fmd is a daemon that runs in the background on each system. fmd receives telemetry information relating to problems detected by the system software, diagnoses these problems, and initiates proactive self-healing activities such as disabling faulty components. When appropriate, the fault manager also sends a message to the syslogd(1M) service to notify an administrator that a problem has been detected. The message directs administrators to a knowledge article on http://illumos.org/msg/, which explains more about the problem impact and appropriate responses.

Each problem diagnosed by the fault manager is assigned a Universal Unique Identifier (UUID). The UUID uniquely identifes this particular problem across any set of systems. The fmdump(1M) utility can be used to view the list of problems diagnosed by the fault manager, along with their UUIDs and knowledge article message identifiers. The fmadm(1M) utility can be used to view the resources on the system believed to be faulty. The fmstat(1M) utility can be used to report statistics kept by the fault manager. The fault manager is started automatically when the operating system boots, so it is not necessary to use the fmd command directly.